The New Zealand Transport Agency plans to phase in a 12-month warrant of fitness from October, nine months earlier than originally planned.

NZTA proposed today that vehicles first registered between 2004 and 2008 would receive a 12-month WoF following their next successful inspection from October 1 this year.

Other changes would come into place next April.

Transport Minister Gerry Brownlee said the changes would save $1.8 billion over 30 years and modernise the 70-year-old WoF inspection system while maintaining road safety.

But Motor Trade Association spokesman Ian Stronach said the shift in the timing was a shock to the industry and the changes would mean a significant reduction in business activity and vehicle safety levels.

"The Government says it is offering these changes to help smooth out the sudden reduction in business that will result from the new WoF frequency regime.

"It won't help industry, but it will allow the Government to showcase an apparent cost-saving to the electorate before next year's election,'' Mr Stronach said.

Cabinet have proposed the following changes to the WoF frequency:

- new vehicles: after initial inspection, no further inspection until vehicles are three years old

- annual inspections for light vehicles three-years-old and older that were first registered anywhere, on or after 1 January 2000

- six-monthly inspections for vehicles first registered anywhere before January 1, 2000

- a greater emphasis on information to encourage motorists to keep their vehicle roadworthy

- additional police enforcement activities.

NZTA have invited feedback on any compliance issues that would need to be considered.